Thermal, Oxidative and CO2 Induced Degradation of Primary Amines Used for CO2 Capture: Effect of Alkyl Linker on Stability

The stability of primary amine grafted mesoporous SBA-15 silica adsorbents with alkyl linker length varying from methyl to propyl (SBA-Methyl, SBA-Ethyl, SBA-Propyl) is investigated with respect to thermal, oxidative, and CO2 induced degradation to assess how differences in stability may result from different chain lengths. Methyl-based materials are found to have no thermal stability, with a severe reduction in amine content of up to 80% upon heating to 135 °C, and were therefore unable to be assessed for oxidative or CO2 specific instabilities. SBA-Ethyl and SBA-Propyl adsorbents are both thermally and oxidatively stable but are prone to urea induced deactivation in the presence of high-temperature, dry CO2 for prolonged periods. A greater extent of CO2 capacity deactivation is observed for SBA-Propyl materials, which is attributed to the larger amine efficiency of the material as compared to that of SBA-Ethyl adsorbents, as this would translate to a greater percentage of amines interacting with CO2 tha...